I would agree with karn, not having nightmares takes away The Dreamer's effectiveness. Not being able to pick up and drop your minions really hinders his play style. If you don't run any nightmares you'll also have a zero soulstone cache, which is never a good thing.
One or two non-nightmares is OK...but I wouldn't through in any more non-nightmares. I'm guessing this question was more along the lines of this and not a full non-nightmare list. Building off what karn said about the Hooded Rider, I think the riders are usually effective in most any list because of their mobility/strength so it could work with the dreamer.